Police block protests in major cities over reforms the opposition says will lead to foreigners acquiring too much land.

Police have detained dozens of protesters in Kazakhstan during anti-government rallies in the country's major cities, prosecutors said.

Opposition activists had called for demonstrations in the Central Asian country's largest cities, including Astana, Almaty and Karagandy, to protest a controversial proposal for land reforms that includes liberalising the sale and rental of farmland to foreigners.

There are fears it could lead to Chinese farmers acquiring large swathes of land.

Authorities had rejected all applications to hold protests on Saturday and cordoned off the main squares of Almaty and Astana, while activists called on their supporters to protest nonetheless.

Kazakhstan's deputy prosecutor general, Andrei Kravchenko, said that as of Saturday, 40 people had been arrested for organising and taking part in these unauthorised demonstrations, TASS news agency reported.

Kravchenko said that the police force had worked to "prevent any violations of the law."

A number of journalists were briefly detained during the protests. Kazakh police later said that the arrests had been a "misunderstanding", Interfax news agency reported.

In April demonstrators had taken to the streets in a string of provincial towns to protest proposed land reforms the government says are important to attract investment into the country.

President Nursultan Nazarbayev earlier this month halted the proposal, saying that "doubts had arisen in society".

A combination of inflation and falling real incomes have fuelled social discontent in a country often regarded as a regional success story despite endemic corruption.

Kazakhstan's tenge currency shed around half its value after the government abandoned a trading corridor with the dollar last year under pressure from low crude prices and Russia's economic downturn.

Land policy is highly politicised in ex-Soviet Central Asia where privatisation policies of the 1990s are often recalled with bitterness and where nearby China is seeking to expand its agricultural interests.